1. Field of the Invention
The present invention refers to a spheric joint (or spherical hinge), in particular for eyeglasses.
A spherical hinge is by definition a joint that enables two rigid segments, which are connected to each other by the hinge itself, to move relative to each other with three rotational degrees of freedom.
2. Description of the Related Art
Owing to their own peculiarities, spherical hinges are used in a large number of different applications.
Patent application FR 2 771 460 describes a lockable spherical hinge used to mount a table between the seats in an aircraft. This spherical hinge consists of a spherical head accommodated in the spherical cavity of a female counterpart piece. The cavity is formed of two members that are joined with each other by means of a linear hinge on the one side and a securing lever on the other side. These two members are in contact with the spherical head via flexible joints. Although this allows an adjustment along three distinct axes, the hinge locking mechanism is complicated in its construction and rather expensive.
Patent application DE 196 01 248 discloses a spherical hinge for use in underwater flash-lamp supports. This hinge includes a spherical-head member that is enclosed in a corresponding cavity of a support. This member is capable of oscillating within a restricted solid angle, as well as rotating about its own longitudinal axis. However, no possibility exists for the spherical-head member to be locked in a fixed position.
Spherical hinges are largely used also in the spectacles manufacturing industry.
It is in fact a widely known fact that the two arms and the frame of a pair of spectacles are generally connected to each other by means of hinges that allow for the arms to be folded back when the spectacles are not being used. The simplest and most well-known solution in this connection lies in having the arms folded parallel to the frame.
Owing to the increasing aesthetical purport of wear items in general, i.e. items that are intended for wearing, spectacles manufacturers are increasingly concentrating on developing and designing most varied and attractive models of spectacles. In particular, a most promising and lively domain in this connection is the one involving the design of hinges for the two arms of the spectacles.
In this connection, patent application JP 080 68 873 describes a spherical hinge having a loop that is made of a filiform, i.e. wire-like material and is bent according to a three-dimensional pattern so as to retain a sphere both above and below the equatorial plane thereof. The sphere itself is attached to a stem and—relative to the loop, which is fixed on the spectacles frame—this stem is capable of rotating both about itself and by an angle of approx. 180° along a narrow equatorial solid angle. This solution, although doing fully away with the use of screws or other fastening means, does however not enable the stem to be locked in any pre-defined position, thereby giving rise to a number of practical drawbacks.
Disclosed in patent application DE 196 29 491 is a spherical hinge adapted to provide a safety coupling between an arm and a frame. The arm has a spherical head, which is received in a corresponding accommodation in the frame, with a linear groove provided therein, in which a pin-like relief member provided within said accommodation is able to slide. When closing the arm by folding it up on the frame, said pin-like member slides along such groove between the two extremities thereof. The arm cannot rotate about itself and can only span an angle of approx. 90°.
Patent application WO 95/10064 describes spectacles, in which each arm is formed of a short member and a much longer one, the latter practically constituting the actual arm. The short member is hinged both on to the spectacles frame—and is able to rotate about an axis passing through the eyes of the wearer—and the longer member along an axis extending perpendicular to the former one. The overall effect of these two hinges is that the two long members can be folded one above and the other below the frame, thereby obtaining a compact structure for the spectacles. This whole set of hinges, however, implies a quite complex and critical construction, especially as far as the locking system for the position of the two segments is concerned, which relies on a small protrusion engaging into a slot, with the possibility of quite easily slipping off therefrom.
Replacing such an articulation system for the spectacles arms with a more simple and effective one would certainly prove quite advantageous.
It therefore is a major object of the present invention to provide a novel spherical hinge, in particular, although not solely, intended for use for the arms of spectacles in view of allowing them to perform particular motions.
Within this general object, it is another purpose of the present invention to provide a hinge for the arms of spectacles that, while enabling the same motions as the hinge disclosed in WO 95/10064, is far more simple and reliable in its construction.